408 stroker hp vs 6.0 LQ9 hp
03-08-2014, 05:12 PM
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408 stroker hp vs 6.0 LQ9 hp How much more hp can i gain by stroking my 6.0 to a 408? Im talkin same set up but just stroking it. So im saying if im at 500 rwhp now about what will it gain me?
03-08-2014, 07:33 PM
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Thanks for the reply. So what would i have to change to get more out of the 408? In my opinion im running good stuff afr 215 heads vwith heavy springs , fast102 intake and tb , c custom grid cam, 60lb injectors msd wires, long tube headers. Would i need a different cam?
03-09-2014, 04:30 AM
#7
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This is the article that inspired my stroker motor build, 5.3 to 383 (6.3). I imagine that many of the same principles apply for a 6.0 to 408 (6.7).
http://www.truckinweb.com/tech/engin...ild/index.html
http://www.truckinweb.com/tech/engin...ild/index.html
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03-09-2014, 08:54 AM
#8
You would need to change the cam and/or cylinder heads to make more power.
Generally speaking, it's all relative to displacement and RPM. For a 364ci engine turning no more than 6200RPM, you have a range of sizes of heads and cam combos that would make good power. Too small of heads and/or cam and power falls off early. Too large, and the power may peak so late that you never really use it.
Bump that 364ci engine up to 408ci, and with the same heads, cam, and bolt ons, it will make pretty much the same power, but the larger displacement causes peak power and torque to occur at a lower RPM. Basically, the old heads and cam would be too small. Now if you were to use a heads and cam combo that was maybe too big for the 364ci, it would be just right with the extra displacement and you will make more power because of the larger ports and longer duration.
Generally speaking, it's all relative to displacement and RPM. For a 364ci engine turning no more than 6200RPM, you have a range of sizes of heads and cam combos that would make good power. Too small of heads and/or cam and power falls off early. Too large, and the power may peak so late that you never really use it.
Bump that 364ci engine up to 408ci, and with the same heads, cam, and bolt ons, it will make pretty much the same power, but the larger displacement causes peak power and torque to occur at a lower RPM. Basically, the old heads and cam would be too small. Now if you were to use a heads and cam combo that was maybe too big for the 364ci, it would be just right with the extra displacement and you will make more power because of the larger ports and longer duration.
03-09-2014, 10:07 AM
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You would need to change the cam and/or cylinder heads to make more power.
Generally speaking, it's all relative to displacement and RPM. For a 364ci engine turning no more than 6200RPM, you have a range of sizes of heads and cam combos that would make good power. Too small of heads and/or cam and power falls off early. Too large, and the power may peak so late that you never really use it.
Bump that 364ci engine up to 408ci, and with the same heads, cam, and bolt ons, it will make pretty much the same power, but the larger displacement causes peak power and torque to occur at a lower RPM. Basically, the old heads and cam would be too small. Now if you were to use a heads and cam combo that was maybe too big for the 364ci, it would be just right with the extra displacement and you will make more power because of the larger ports and longer duration.
Generally speaking, it's all relative to displacement and RPM. For a 364ci engine turning no more than 6200RPM, you have a range of sizes of heads and cam combos that would make good power. Too small of heads and/or cam and power falls off early. Too large, and the power may peak so late that you never really use it.
Bump that 364ci engine up to 408ci, and with the same heads, cam, and bolt ons, it will make pretty much the same power, but the larger displacement causes peak power and torque to occur at a lower RPM. Basically, the old heads and cam would be too small. Now if you were to use a heads and cam combo that was maybe too big for the 364ci, it would be just right with the extra displacement and you will make more power because of the larger ports and longer duration.
03-09-2014, 11:16 AM
#11
Bump that 364ci engine up to 408ci, and with the same heads, cam, and bolt ons, it will make pretty much the same power
I say this because I always hear people say X heads are good for a 4" bore 364, but too small on a 4" bore 402. And I think to myself, if why would the heads be enough to fill a 364 but not a 402 of the same bore as long as you keep the valve events the same for both setups? All you're changing is how long the stroke is, so by compensating that with an equivalent increase in valve timing then it shouldn't be a problem for the same heads to fill in the cylinder equally.
03-09-2014, 03:00 PM
#12
Thanks for the reply. So what would i have to change to get more out of the 408? In my opinion im running good stuff afr 215 heads vwith heavy springs , fast102 intake and tb , c custom grid cam, 60lb injectors msd wires, long tube headers. Would i need a different cam?
I had TFS 215 heads, Fast 90/90 intake, 234/242/114+4 cam, 1.75 LG Pro headers, 3" cats, 3" cat back on my 2001 ZO6 short block.
I have since installed a TSP 418 short block. I unshrouded the valves to match my bore and milled .005 of the heads to bring the cc back to 63 (11.5 CR). Reused the same cam, but installed it at 114 to shift the power band up. Never had it on a dyno, but the car gained huge power! The 346 took 12.5 sec to go from 18 mph to 106 mph in 3rd gear. As that is how I tune the AFR on manual trans vehicles. The 418 18-106 is 9.5 sec!
I've since installed a 234/242/.600/.615 117+2 cam as I hated the drive ability of my old 10* overlap cam. This cam still has stupid bottom end power and pulls harder mid range to top end due to the earlier exhaust valve opening.
Several "experts" were trying to convince me that I needed a bigger "stroker" cam, bigger headers, bigger heads etc.
Russ Kemp
03-09-2014, 04:43 PM
#13
But where the game changes with the increase in crankshaft length is the faster piston speed, so things happen a little faster than your standard 3.622 stroke. Then you have to reevaluate your timing events.
03-09-2014, 06:17 PM
#14
What if for example you keep the same heads, but you increase the cam duration to have the same exact valve events as in the smaller engine?
I say this because I always hear people say X heads are good for a 4" bore 364, but too small on a 4" bore 402. And I think to myself, if why would the heads be enough to fill a 364 but not a 402 of the same bore as long as you keep the valve events the same for both setups? All you're changing is how long the stroke is, so by compensating that with an equivalent increase in valve timing then it shouldn't be a problem for the same heads to fill in the cylinder equally.
I say this because I always hear people say X heads are good for a 4" bore 364, but too small on a 4" bore 402. And I think to myself, if why would the heads be enough to fill a 364 but not a 402 of the same bore as long as you keep the valve events the same for both setups? All you're changing is how long the stroke is, so by compensating that with an equivalent increase in valve timing then it shouldn't be a problem for the same heads to fill in the cylinder equally.
With the longer stroke, there is more volume pulling on the same area at a faster rate. It's like a syringe. If you pull it just a little bit in X amount of time, you may not even really feel the vacuum. Try to pull the plunger all the way in the same amount of time, and you can feel the resistance from the vacuum in the syringe.
For the same area, this larger negative pressure increases the air speed in the port (ie Bernoulli's Law) at any given RPM. If the airspeed is too fast, you get turbulence and separation around the bends and corners of the port and the cylinder won't be filled efficiently, even with more time. This is why the peak torque is at a lower RPM because at peak torque, the port velocity is at a "sweet spot" and is filling the cylinder most efficiently and that velocity "sweet spot" is now happing at a lower RPM with the increase in displacement. Opening the port for the larger displacement slows down that airspeed so that the "sweet spot" occurs at a higher RPM.
03-09-2014, 06:24 PM
#15
Jim McFarland published a book with a formula for establishing the MCSA for a given RPM and displacement.
MCSA in Square Inches = (Cylinder Volume in Cubic Inches x Peak Torque RPM) / 88,200
03-09-2014, 07:09 PM
#16
Opening the port for the larger displacement slows down that airspeed so that the "sweet spot" occurs at a higher RPM.
For example, a TFS casting with 225cc intake port will make more power than an AI 243 casting with their 232cc intake port. So even though the port is larger on the 243 head, it will make less power. So there's something else also that decreases this "turbulance" much more so than the size of the port.
03-10-2014, 02:25 PM
#18
But the intake stroke is not the most important aspect that many concentrate on. The EVO is important as well especially with a faster piston speed. Yes you could use the same cam but for bench racing, we are usually speaking interms of maximum effciciency and with the added piston speed I would like an earlier EVO. IMO. Others can do what they want.
I think you read what I stated but did not read into it.
As I stated, the cylinder does not care about port shape, size or brand. I stand behind that. I am not going to get into a long monologue about it, but the cylinder is not biased, people are. Most of these biases only exist in the minds of people vs. actual concrete physics and lost with interpretations forshadowed by marketing.
Once many think in that context, then they will no longer have biases to a certain head as an alixer meaning that would end the cathedral vs square port feud. Because the real players in the game know that you can make power with both.
They told you guys here for years that you needed small ports and the 220cc head was considred large. They had all of these guys parroting the same thing. Then gm came out with the 257cc head, and now every aftermarket company has increased their cc sizes. 230,235,237,245,247, etc..
Yes the optimal CSA is one conversation and the ability to still make power without the optimal CSA is another.
As I stated, the cylinder does not care about port shape, size or brand. I stand behind that. I am not going to get into a long monologue about it, but the cylinder is not biased, people are. Most of these biases only exist in the minds of people vs. actual concrete physics and lost with interpretations forshadowed by marketing.
Once many think in that context, then they will no longer have biases to a certain head as an alixer meaning that would end the cathedral vs square port feud. Because the real players in the game know that you can make power with both.
They told you guys here for years that you needed small ports and the 220cc head was considred large. They had all of these guys parroting the same thing. Then gm came out with the 257cc head, and now every aftermarket company has increased their cc sizes. 230,235,237,245,247, etc..
Yes the optimal CSA is one conversation and the ability to still make power without the optimal CSA is another.
03-10-2014, 02:31 PM
#19
But port size is not the only answer to power tho.
For example, a TFS casting with 225cc intake port will make more power than an AI 243 casting with their 232cc intake port. So even though the port is larger on the 243 head, it will make less power. So there's something else also that decreases this "turbulance" much more so than the size of the port.
For example, a TFS casting with 225cc intake port will make more power than an AI 243 casting with their 232cc intake port. So even though the port is larger on the 243 head, it will make less power. So there's something else also that decreases this "turbulance" much more so than the size of the port.
Also, a 225cc port and a 232cc port may not have the cross sections you would expect. The MCSA of my 241 heads are 90% of the valve diameter and its still only a 209cc port. Port volumes are not reliable indicators of the real size of the port as far as the engine is concerned.
03-10-2014, 04:22 PM
#20
If you pull it just a little bit in X amount of time, you may not even really feel the vacuum. Try to pull the plunger all the way in the same amount of time, and you can feel the resistance from the vacuum in the syringe.